The present invention relates to an air volume flow and pushing force control device for a vacuum cleaner that has at least a motor, a dust receptacle and a suction nozzle, comprising a controller for controlling the motor power, and a first sensor, for detecting the air volume flow, which in conjunction with the controller forms a first control loop in order to maintain the air volume flow at a prescribed air volume flow value on the basis of the signal of the first sensor.
Air volume flow control devices for vacuum cleaners are generally known. They are used for the purpose of maintaining the air volume flow constant at a prescribed value, independently of the filling level of a dust bag present in the vacuum cleaner. Without such a control, with an empty dust bag the air volume flow would be very high because of the low resistance, whereas it would be correspondingly low with a filled dust bag. This would lead to different suction results, something which is not desired. Moreover, the air volume flow control is advantageous from the point of view of energy, since it is possible to operate at a lower motor power with an empty dust bag.
The air volume flow can be detected, for example, by measuring the pressure between the dust bag receptacle and the motor. Since the pressure bears a fixed relationship to the air volume flow, the air volume flow can be inferred via this measurement. If this pressure varies, the control proceeds on the assumption that the dust bag has been filled, and in reaction thereto the motor power of the motor is raised in order to keep the air volume flow constant.
The air volume flow control of the abovenamed type also responds when the air volume flow is reduced not by the filling of the dust bag, but, for example, by virtue of the fact that the suction nozzle has been brought onto a soft underlying surface, for example a soft dense carpet. In this case, as well, the control attempts to keep the air volume flow constant and therefore raises the motor power. However, the consequence of this is that the force required to move the suction nozzle, which is referred to below as pushing force, increases, and therefore hampers the use of the vacuum cleaner.